Magnetic pulley for removal of non-magnetic pieces from waste material

ABSTRACT

A technique of removing electrically conductive nonmagnetic particles from a stream of material by a cylindrical magnet driven by a conveyor belt carrying the stream of material wherein attractor windings are provided in conjunction with excitation windings for forming zones of attraction of electrically conductive non-magnetic particles to the magnet. Electrically non-conductive and non-magnetic particles are thus not attracted to the magnet and are free to follow a different path than are the electrically conductive non-magnetic particles. Separation is thus achieved between them.

United States Patent 1191 Benowitz 1 1 MAGNETIC PULLEY FOR REMOVAL OF NON-MAGNETIC PIECES FROM WASTE MATERIAL [75] lnventor: Sander Benowitz, Sunnyvale, Calif.

[73] Assignee: Combustion Power Company, Inc.,

Menlo Park, Calif.

[22] Filed: Sept. 17, 1973 [21] Appl. No.: 397,637

[52] 11.8. C1. 209/213; 209/219; 209/223 A [51] Int. Cl. 303C 1/18 [58] Field of Search 209/219, 223 A, 212, 227,

[56] References Cited UNITED STATES PATENTS 567,382 9/1896 Eickemeyer 209/219 676,841 6/1901 Edison 209/219 X 714,256 11/1902 Sutton 1,371,301 3/1921 Converse 209/219 1,414,170 4/1922 Bethke 209/223 A X 1,416,634 5/1922 Mull 209/212 1,417,189 5/1922 McCarthy 209/212 1,842,851 1/1932 Ollrim 209/219 1 July 1, 1975 2,400,869 5/1946 Lovell 335/250 3,054,026 9/1962 Lovell 335/244 X 3,447,469 6/1969 Laing 310/166 X FOREIGN PATENTS OR APPLICATIONS,

622,786 3/1927 France 335/289 Primary Examiner-Robert Halper Attorney, Agent, or Firm-Limbach, Limbach & Sutton [5 7] ABSTRACT A technique of removing electrically conductive nonmagnetic particles from a stream of material by a cylindrical magnet driven by a conveyor belt carrying the stream of material wherein attractor windings are provided in conjunction with excitation windings for forming zones of attraction of electrically conductive non-magnetic particles to the magnet. Electrically non-conductive and non-magnetic particles are thus not attracted to the magnet and are free to follow a different path than are the electrically conductive non-magnetic particles. Separation is thus achieved between them.

12 Claims, 6 Drawing Figures PATENTEDJULI 1915 w 8 92,6 58 SHEET 1 1 MAGNETIC PULLEY FOR REMOVAL OF NON-MAGNETIC PIECES FROM WASTE MATERIAL CROSS-REFERENCE TO A RELATED APPLICATION The subject matter of this application is related to that of copending application Ser. No. 329,587 now U.S. Pat. No. 3,824,516. filed Feb. 5, 1973 by the applicant herein.

BACKGROUND OF THE INVENTION This invention is related generally to electromagnetic separation methods and apparatus and more specifically to electromagnetic devices of a magnetic pulley type.

The recent emphasis on re-cycling and re-use of waste material as much as possible has created a need for removing from garbage and other waste material its more valuable components. There have been many recent advances in solid state waste processing techniques. A first step in such waste processing techniques is generally to shred the incoming raw waste material for reducing the physical size of its particles. The shredded waste material is then passed through an air classifier for removal of the light fractions such as paper. The heavier fractions, such as metal, glass, wood, rubber, plastic, and rock remain for separation into their various constituents. Ferrous metals are easily removed with existing magnetic equipment. The most popular commerically available equipment for this purpose utilizes a cylindrical magnet that is rotatable about the axis of the cylinder and whose outside acts as a pulley for a conveyor belt which carries material to be separated which is usually the heavier fractions of the waste material. The ferrous metals are attracted to the cylindrical magnet while the non-magnetic materials are either not affected or affected very little. Therefore, it is possible to change the path of the magnetic particles from the normal gravity influence path of the nonmagnetic particies.

included in the non-magnetic particle components are electrically conductive particles; that is, particles of non-magnetic metals such as copper and aluminum. It has been suggested in US. Pat. No. 3,448,857 Benson et al. (1969) that a subsequent magnetic pulley stage can be utilized for removing the non-magnetic metals from the heavy particles that remain after ferrous metal magentic separation. The Benson et al patent suggests the use of a high speed rotating magnet within a cylinder over which a conveyor belt travels. This type of magnetic pulley suffers from significant disadvantage by being mechanically complex in an interface structure between a rotating magnet that necessarily moves at a much higher speed than an associated conveyor belt in order to affect the non-magnetic metais. The Benson et al patent also suggests a high energy pulsed electromagnet that remains stationary with respect to the waste material carrying conveyor. In both the permanent magent and electromagent embodiments suggested by Benson et al there is a significant disadvantage in that the non-magnetic metals are repulsed rather than being attracted to the conveyor belt. Since the repulsion distance that is practically obtainable is limited and not predictable, the paths of the non-magnetic metal and the other waste material are not made significantly different enough that one can be easily and completely separated from the other.

Accordingly, it is an object of the present invention to provide a magnetic pulley type of separator for nonmagnetic metals that is mechanically simple and which provides a more substantial physical separation of the non-magnetic metal particles from the other materials in the stream of material.

It is among the other objects of the present invention to provide an electromagnetic technique for separating non-magnetic metals from a stream of material that consumes a low amount of electrical power and which does not produce excessive heat.

SUMMARY OF THE INVENTION Briefly, these and additional objects are accomplished by the present invention wherein means for guiding shredded waste material, such as a conveyor belt, is provided for movement of the shredded material by an electromagnetic element which attracts nonmagnetic metal particles toward it while not affecting non-metals such as glass, wood, rubber, plastic and rock. The electromagnet is preferably in the form of a cylinder which acts as a pulley for the conveyor belt so that the non-metal particles fall off the end of the conveyor by gravity where the conveyor belt wraps around the magnet while the non-magnetic metal particles remain attached to the conveyor belt until it travels under the cylindrical magnet. A very substantial physical separation of the non-magnetic metal from non-metal particles is thus accomplished and the non-magnetic metals are recovered from the waste material. If there are magnetic particles in the waste material as well they will also be attracted to the electromagnet but it is preferable that the magnetic metal particle be removed by conventional equipment in a stage prior to the stage utilizing the present invention to remove non-magnetic metals from the waste material.

The electromagnet cylinder includes a plurality of electromagnetic poles (reaction Zones) that each have an alternating current driven excitator winding or windings physically positioned adjacent to an attractor electrical current path or paths which can be a short circuited turn, short circuited coil or a winding with phase shifting elements in series therewith, or one that is driven by a separate phase controlled electrical source. The different current phases in the excitor and attractor elements usually about results in similarly out of phase magnetic fields overlapping one another adjacent the surface of the cylinder in a manner to form an attraction zone for non-magnetic metal particles. Alternately, the electromagnets may include more than one coil or winding positioned so as to distribute the zones of influence over larger areas. It is believed that the eddy currents generated in a nonmagnetic electrically conductive particle by the excitor winding is in the same direction as those currents flowing in the attractor loop, thereby forming an attraction between the attractor loop and the non-magnetic metal particle. The use of an attractor winding for other nonmagnetic metal attraction is described in US. Pat. Nos. 2,400,869 Lovell (1946) and 3,054,026 Lovell (1962).

Additional objects, advantages and features of the various aspects of the present invention may be had by reference to the foilowing description of its preferred embodiments which should be taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the primary elements of an electromagnetic separation system according to one embodiment of the present invention.

FIG. 2 shows the electromagnet of FIG. 1 with a conveyor belt removed;

FIG. 3 illustrates a variation of the embodiment of FIG. 1;

FIG. 4 illustrates yet another variation of the embodiment of FIG. 1;

FIG. 5 shows a cylindrical magnet according to another embodiment of the present invention; and

FIG. 6 illustrates a use of the cylindrical magnet of FIG. 5 with a conveyor belt.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, one embodiment of the present invention will be described. A conveyor belt 11 passes over a cylindrical electromagnetic structure 13 which is held to rotate about a center line of the cylinder which passes through the center of a shaft 15. The conveyor 11 is driven by a motor source (not shown) and carries a stream of shredded waste material toward the cylindrical magnet 13 as shown in FIG. 1. The cylindrical magnet 13 is rotated by its frictional engagement at its outside surface with the under side of the conveyor belt 1 1. The non-metal particles of the stream of waste material carried on the conveyor 11 will fall off of the conveyor as it turns under the magnet 13. The path of such non-metal particles (including glass, plastic, and wood, etc) is indicated by an arrow 17. Metal particles, on the other hand, are attracted toward the magnet 13 and held against the conveyor belt 11 until they are forced to drop from a position under the magnet 13 wherein the forces of gravity exceed the magnetic attraction forces. The metal particles travel in a path indicated generally by the arrow 19 of FIG. 1. A physical barrier 21 is schematically illustrated in FIG. 1 for separating the non-metal from the metal particles.

As explained previously, it is preferred that the ferrous or magnetic metals have been previously removed from the material so that the stream carried by the conveyor 11 includes a very small proportion, if any, of magnetic metal particles. Since it is desired to separate the magnetic metals from the non-magnetic metals, it is preferred that the magnetic metals have been removed at an earlier stage prior to the separation illustrated in FIG. 1. Therefore, the only metals included in any significant quantity in the material on the conveyor 1 1 are of the non-magnetic type, such as copper or aluminum, and thus are diverted in a distinct path indicated by the arrow 19 upon influence of the cylindrical magnet 13.

The cylindrical magnet 13 is formed of a laminated magnetic core structure wherein a large number of identical ferro-magnetic discs are held together. The discs are circular in shape with various notches provided at their outside circumference for acceptance of the magnetic excitation and attracting coils. In the embodiment of FIGS. 1 and 2, there are eight separate electromagnets positioned around the outside surface of the cylinder, including the three identified magnets 23, 25, and 27. These three magnets are shown in a partial view of the cylinder 13 in FIG. 2 wherein they may be viewed without the obstruction of the conveyor 11. Each of these three electromagnets has its own pole face. The exciting coil 35 is wound in the middle slots 37 and 39 of the set of three adjacent slots on either side of its pole face 31. It will be noted that the excitation coils for the adjacent magnets 23 and 27 share the same slots 37 and 39 in a manner to overlap the excitation coils. The currents of adjacent excitation coils as shown by the arrows on these coils in FIG. 1 are made to flow in opposite directions and thus these coils share the same magnetic return path. All of the excitation coils of the cylindrical magnet may be connected to a common two terminal single phase alternating current source by which the phase of excitation coils on adjacent poles is reversed.

An attractor electrical current path 41 is looped around the pole face 31 in slots 43 and 45. Additional slots 47 and 49 are provided immediately adjacent the surrounding pole faces 29 and 33 and are provided for receiving the attractor electrical current path associated with each of those pole faces. Each of the attractor electrical current paths such as the loop 43 may be a closed electrical conductor loop of a single or multiple turns. The result is that the magnetic field generated by the excitation winding 35 induces a current in the attractor current path 41 that is about l80 out of phase with that and the exciting winding 35. This is the same phase relationship that exists between current in the exciting winding 35 and some non-magnetic electrically conductive particle that is carried by the conveyor belt 1 1. Therefore, the magnetic fields generated by current induced in such a particle and in the attractor loop 41 are substantially the same phase and will thus be attracted to one another. This attraction mechanism for non-magnetic metals forms a zone or volume of attraction 51 as indicated in dotted outline in FIG. 1. Each of the 8 separate adjacent electromagnets of the cylindrical electrical magnet 13 produces its own separate zone of attraction. Between adjacent zones of attraction, there exists areas where non-magnetic metal particles will be repelled from the conveyor, such as the narrow areas 53 and 55 surrounding the zone of attraction 51. By providing multiple electromagnets and by overlapping their excitation coils, however, the dead or particle repelling areas are made very small. Additionally, if a non-magnetic metal particle is predominately within a zone of attraction and partially without the zone, there are forces which tend to pull it into the zone of attraction. It will additionally be noticed from FIG.

2 that the excitation coils and the associated attractor electrical paths are in planes substantially parallel with the axis of rotation of the cylinder. Also, there is one attractor winding for each magnet; that is, one attractor current path for every excitation winding.

There are many variations in the form of the attractor current path 41 which may be employed. For instance, some current carrying metal may be utilized other than normal electrical wire to form a short circuit path. An example is one or more washers positioned to conduct current in a plane parallel to that of the associated excitation Winding. Additionally phase shifting equipment may be placed in series with the attractor current path in order to optimize the attraction of non-magnetic metals. As another means of optimizing the attraction forces, the attractor winding 41 may be supplied by an independently phase controllable electrical source so that the relative phase of the current flowing therein may be controlled with respect to the phase of the current flowing in the associated excitation winding, such as the winding 35, to maximize the attraction forces of non-magnetic metal particles. The currents induced in such a particle by the excitation winding 35 generate a magnetic field that is in phase with the magnetic field generated by the attractor winding such as the winding 41. The relative phase angle between the currents flowing in the attractor and excitation windings for this maximum attraction capability depends essentially on the relationship between the inductances and resistances of the two windings.

The illustration of FIGS. 1 and 2 shows a single excitation coil and a single attractor winding or turn associated with each magnetic pole. It will be understood, of course, that the excitation and/or attractor elements associated with each pole may include two or more windings that cooperate to produce that poles reaction zone as described.

In order to maximize the flux densities and thus the attraction capabilities of such an electromagnet, the excitation windings are driven at a current level as high as possible without generating an excessive amount of heat. In order to maximize the attracting current which may be applied to the electromagnets, the cylindrical magnet may be cooled or could be intermittently operated by pulsing. Pulsing is not desirable, however, because the electromagnet would fail to perform separation during the periods between pulses. However, it will be noted from FIG. 1 that when the individual electromagnets of the cylindrical magnetic structure 13 are out of contact with the conveyor belt 11 that they are not needed in the separation process. That is, the electromagnets are not doing any work when they are positioned away from the conveyor belt 11. Therefore, they may be turned off during this segment of their rotation and thus reduce the amount of heat that is generated. Each individual electromagnetic circuit may be controlled with semiconductor switches such as Triacs mounted on the magnetic pulley so that the energization and de-energization of each excitation winding is controlled in a sequence synchronized with the pulley travel. Sensors such as light sources or magnetically operated reed switches may be used to generate synchronizing signals for controlling the switching function.

A simplified method of minimizing the heating problem is illustrated in FIG. 3 and 4. Referring to FIG. 3, metal laminations 51 are formed in a cylindrical shape having a center at the center rotation and extending about 120 around the circumference. The result is that the current is automatically reduced in each of the electromagnets as they travel through a region opposite the ferrous metal laminated structure. The laminated magnetic member 51 forms a part of the flux return path of electromagnets that are positioned opposite this to form a low reluctance magnetic circuit. Therefore, the electrical impedence of the windings in these portions of travel increases and the current therein is automatically reduced.

In order to increase the zone in which the electromagnets are operating at a reduced current, the belt angle may be changed as illustrated in FIG. 4 wherein a cylindrically shaped laminated ferrous metal member extends almost 180 around the path of the cylindrical electromagnet. Additional cooling of the electromagnet is obtained at the expense of the moving the path 19 of the desired non-magnetic metal particles closer to the path 17 of non-metal particles.

It will be noted from FIGS. 3 and 4 that the metal particles to be separated fall from the under side of the conveyor belt 11 as they are moved away from the electromagnet 13. It should also be noted that the metal particles that are drawn down tightly against the conveyor belt 11 under the influence of the electromagnet will move at the same speed as the speed of the conveyor 11 and the electromagnetic field movement. It is desired that the travel of the electromagnetic fields (zones of attraction) have no relative velocity with respect to the conveyor 11 so that energy is not wasted in moving metal particles with respect to the conveyor belt.

Another embodiment of an electromagnetic pulley is illustrated in FIGS. 5 and 6. A cylindrical magnet 65 whose large number of circular ferrous metal sheets are laminated together about a rotation shaft 67. The large diameter circular laminations form walls such as the walls 69 and 71, which'are held spaced apart by smaller diameter stacked laminations such as the laminations spaced between the walls 71 and 73. Thus a series of spools are formed adjacent one another along the length of the cylindrical magnet. Every third spool is provided with an excitation winding such as windings 77, 79 and 81 of FIG. 5. Attractor windings are formed in the remaining spools, such as the attractor windings 83, 85, 87 and 89 of FIG. 5. The attractor windings are either short circuited, placed in series with some phase shifting mechanism or independently driven to control the phase relative to that of the excitation windings, as discussed generally above. The excitation windings 77, 79 and 81 are connected to the same single phase alternating current source in a manner that the polarity of current flow of adjacent attractor windings, such as the windings 77 and 79, is opposite as indicated by the arrows of FIG. 5. The electromagnet of FIG. 5 may be viewed as having a plurality of electromagnets each having an excitation winding and an attractor current path but with the excitation winding polarity as described it is possible for one physical excitation winding to serve as excitation for adjacent at tractor windings on either side thereof. That is, for example, the excitation winding 79 operates in conjuction with the attractor windings and 87 on either side thereof, as if the excitation windings 79 were in fact two separate coils one of which is operating with a distinct attractor winding. Two such excitation coils could be used, of course, but is simpler to use a single physical excitation coil to serve the function of two.

The magnet of FIG. 5 generates zones of attraction 91 and 93 which attract non-magnetic metal particles while repulsing such particles if they lie wholly outside of these zones. As mentioned above, however, if a particle has a majority of its area within one of these zones and the remaining area outside thereof, there are forces which operate to move the non-magnetic metal particle within a zone of influence resulting in it then being attracted through the magnet. These zones of attraction 91 and 93 extend completely around the magnet. The magnets and the resulting zone of attraction are oriented perpendicularly to an axis of rotation at the center of the cylinder as opposed to the embodiment described with respect to FIGS. 1 and 2 wherein the coils and zones of attraction extend generally parallel to the cylindrical magnet axis of rotation.

Of course, other specific excitation and attraction winding arrangements are possible in the embodiment of FIG. 5, such as additional cooperating coils to form the desired magnetic poles and resulting magnetic reaction zones that cooperate to form the zones of attraction 91 and 93.

A preferred use of the magnet of the type illustrated in FIG. is shown in FIG. 6 with a conveyor belt 95. It will be noted from FIG. 5 that the attraction zones 91 and 95 are not interrupted around the cylindrical magnet with repulsion areas. Rather, such particles will be repelled only when outside of one of these zones of attraction 91 and 93 in an axial direction. Therefore, the preferred use of such a magnet as shown in FIG. 6 includes the addition of mechanical guides 97, 99 and 101 above the conveyor belt 95 to channel all of the material being carried thereby into two spaced apart streams 103 and 105 which are within the zones of attraction 91 and 93. With such a system, there are no dead or repulsive areas in which the waste material flows. Of course, a commerical embodiment includes a larger number of zones of attraction but only two have been illustrated herein for simplicity. The additional zones of attraction are obtained by adding on to the electromagnet of FIG. 5 a number of additional exciting and attractor windings which conform to the requirements discussed above.

It is additionally possible with the configuration of FIG. 6 to alternately divert a single stream of waste particles between a plurality of attraction zones while simultaneously switching off the unused attraction zones. This would permit large amounts of currents to be run through a single exciting winding at any one time without heating device as much as if all attraction zones were operated simultaneously.

Although the various aspects of the present invention have been described with respect to its preferred embodiments, it will be understood that the invention is entitled to protection within the full scope of the appended claims.

I claim:

I. Apparatus for separating electrically conductive non-magnetic objects from a mixture including other types of objects, comprising:

means for guiding said mixture in a stream past a separation station,

magnetic means positioned adjacent said stream guiding means at said separation station for attracting said electrically conductive non-magnetic objects from said mixture as it passes thereby, said magnetic means including a plurality of electromagnetic assemblies positioned adjacent each other across the surface of said magnetic means and each having an excitation coil and an attractor current path electrically isolated from one another but arranged to be magnetically coupled in a manner that their magnetic fields overlap to produce a zone of attraction of non-magnetic particals when currents in said excitation coil and said attractor current path are out of phase, means for removing the attracted objects from the influence of said magnetic means and means for collecting objects after removal from said magnetic means, whereby said electrically conductive non-magnetic objects have been separated from said stream.

2. The apparatus of claim 1 wherein said magnetic means is cylindrical in shape and mounted to be rotatable about its axis, said cylindrical magnetic means being positioned relative to said mixture guiding means so that the stream of the mixture moves in a path about a portion of an outside surface of the cylindrical magnetic means in a direction of rotatability of the outside surface.

3. Apparatus according to claim 2 wherein the attractor current path of each of said electromagnetic assemblies is positioned in slots adjacent the surface of the cylindrical magnet wherein a core of said cylindrical magnet is a ferromagnetic material and the attractor winding an excitor coil of each of the plurality of electromagnetic assemblies are positioned parallel to the axis of rotation of said cylindrical coil within slots of said magnetic material core into the cylindrical surface which extend along its length.

4. Apparatus according to claim 3 wherein each of said electromagnetic assemblies additionally includes a pair of spaced apart parallel slots in which the attractor electrical current path is positioned with said excitor coil being formed in a pair of slots adjacent and parallel to said attractor current loop slots but to the outside thereof, said pair of excitor coil slots of each said electromagnetic assemblies additionally receiving a portion of the excitation coils of the electromagnetic assemblies on either side thereof, whereby the zones of attraction of non-magnetic metal are formed substantially continuously around said cylinder with only small areas of repulsion between each of said zones of attraction.

5. Apparatus according to claim 2 wherein said cylindrical magnet comprises:

a large number of circular magnetic material sheets held together at their center at the axis of rotation and perpendicular thereto, such sheets having two distinct diameters and being arranged to form a plurality of spools along the length of the cylindrical magnet that are separated by walls of the larger diameter magnetic discs,

a plurality of exciting windings contained individually in every third spool along the length of said cylindrical magnet, said excitor windings being electrically connected so that current flows in opposite directions in adjacent excitor windings, and

an attractor windings in each of the spools contained between two of said excitor windings, whereby a zone of attraction of non-magnetic metal pieces is formed around said cylindrical magnet across said attractor windings with repulsion areas between said attraction zones.

6. Apparatus according to claim 2 which additionally comprises magnetic material positioned immediately adjacent substantially all of the cylindrical magnet outside surface over which waste material does not travel, whereby the current in said excitor windings is reduced when in the region of said magnetic path material.

7. Apparatus for separating non-magnetic metal pieces from a mixture including other types of objects, comprising:

a cylindrical magnet characterized by a plurality of zones of attraction of non-magnetic metal pieces toward said cylindrical magnet, said zones covering a significant amount of the outside surface of said cylindrical magnet, said cylindrical magnet including a plurality of electromagnetic assemblies positioned adjacent one another across the surface of said cylindrical electromagnet, each of said electromagnetic assemblies including an excitation coil and an attractor electrical current path electrically isolated from one another but arranged to be magnetically coupled and to have a region adjacent the cylindrical surface where magnetic fields therefrom overlap to produce one of said zones of attraction when currents in said excitation coil and said attractor electrical current path are out of phase, and

a flexible elongated conveyor contacting at least a portion of the outside surface of said cylindrical magnet in a manner to change conveyor direction and also in a manner to rotate said magnet in response to linear motion of the conveyor, whereby non-magnetic metal pieces within a mixture including other types of objects are drawn against said conveyor belt at its region contacting said cylindrical magnet while certain other types of objects are not.

8. Apparatus for separating non-magnetic metal pieces from a mixture including other types of objects, comprising:

a cylindrical magnet characterized by a plurality of zones of attraction of non-magnetic metal pieces toward said cylindrical magnet, said zones covering a significant amount of the outside surface of said cylindrical magnet, said cylindrical magnet including a plurality of electromagnetic assemblies positioned adjacent one another across the surface of said cylindrical electromagnet, each of said electromagnetic assemblies including an excitation coil and an attractor electrical current path electrically isolated from one another but arranged to be magnetically coupled and to have a region adjacent the cylindrical surface where magnetic fields therefrom overlap to produce one of said zones of attraction when currents in said excitation coil and said attractor electrical current path are out of phase,'the attractor current path of each of said electromagnetic assemblies being positioned in slots adjacent the surface of the cylindrical magnet wherein a core of said cylindrical magnet is a ferromagnetic material and the attractor current path and excitation coil of each of the plurality of electromagnetic assemblies are positioned parallel to an axis of rotation of said cylindrical coil within slots of said magnetic material core into the cylindrical surface which extend along its length, and

a flexible elongated conveyor contacting at least a portion of the outside surface of said cylindrical magnet in a manner to change conveyor direction and also in a manner to rotate said magnet in re sponse to linear motion of the conveyor, whereby non-magnetic metal pieces within a mixture including other types of objects are drawn against said conveyor belt at its region contacting said cylindrical magnet while certain other types of objects are not,

9. Apparatus according to claim 8 wherein each of said electromagnetic assemblies additionally includes a pair of spaced apart parallel slots in which the attractor electrical current path is positioned with said excitor coil being formed in a pair of slots adjacent and parallel to said attractor current loop slots but to the outside thereof, said pair of excitor coil slots of each said elec- Elli tromagnetic assemblies additionally receiving a portion of the excitation coils of the electromagnetic assemblies on either side thereof, whereby the zones of attraction of non-magnetic metal are formed substantially continuously around said cylinder with only small areas of repulsion between each of said zones of attraction.

10. Apparatus for separating nonmagnetic metal pieces from a mixture including other types of objects, comprising:

a cylindrical magnet characterized by a plurality of zones of attraction of non-magnetic metal pieces toward said cylindrical magnet, said zones covering a significant amount of the outside surface of said cylindrical magnet, said cylindrical magnet comprising:

a large number of circular magnetic material sheets held together at their center at the axis of rotation and perpendicular thereto, such sheets having two distinct diameters and being arranged to form a plurality of spools along the length of the cylindrical magnet that are separated by walls of the larger diameter magnetic discs,

a plurality of exciting windings contained individually in every third spool along the length of said cylindrical magnet, said excitor windings being electrically connected so that current flows in opposite directions in adjacent excitor windings, and

an attractor windings in each of the spools contained between two of said excitor windings, whereby a zone of attraction of nonmagnetic metal pieces is formed around said cylindrical magnet across said attractor windings with repulsion areas between said attraction zones, and

a flexible elongated conveyor contacting at least a portion of the outside surface of said cylindrical magnet in a manner to change conveyor direction and also in a manner to rotate said magnet in response to linear motion of the conveyor, whereby non-magnetic metal pieces within a mixture including other types of objects are drawn against said conveyor belt at its region contacting said cylindrical magnet while certain other types of objects are not.

11. Apparatus according to claim it) which additionally comprises:

diverters adjacent said conveyor upstream of said cylindrical magnet, said mechanical diverters positioned to form a stream of material mixture into individual streams that pass over said cylindrical magnet within its zones of attraction of nonmagnetic metal particles.

12, Apparatus for separating non-magnetic metal pieces from a mixture including other types of objects, comprising:

a cylindrical magnet characterized by a plurality of zones of attraction of non-magnetic metal pieces toward said cylindrical magnet, said zones covering a significant amount of the outside surface of said cylindrical magnet,

a flexible elongated conveyor contacting at least a portion of the outside surface of said cylindrical magnet in a manner to change conveyor direction and also in a manner to rotate said magnet in response to linear motion of the conveyor, whereby non-magnetic metal pieces within a mixture includsurface that is not contacted by said conveyor belt, whereby the current in said excitor windings is reduced when in the region of said magnetic path material. 

1. APPARATUS FOR SEPARATING ELECTRICALLY CONDUCTIVE NONMAGNETIC OBJECTS FROM A MIXTURE INCLUDING OTHER TYPES OF OBJECTS, COMPRISING: MEANS FOR GUIDING SAID MIXTURE IN A STREAM PAST A SEPARATION STATION, MAGNETIC MEANS POSITIONED ADJACENT SAID STREAM GUIDING MEANS AT SAID SEPARATION STATION FOR ATTRACTING SAID ELECTRICALLY CONDUCTIVE NON-MAGNETIC OBJECTS FROM SAID MIXTURE AS IT PASSES THEREBY, SAID MAGNETIC MEANS INCLUDING A PLURALITY OF ELECTROMAGNETIC ASSEMBLIES POSITIONED ADJACENT EACH OTHER ACROSS THE SURFACE OF SAID MAGNETIC MEANS AND EACH HAVING AN EXCITATION COIL AND AN ATTRACTOR CURRENT PATH ELECTRICALLY ISOLATED FROM ONE ANOTHER BUT ARRANGED TO BE MAGNETICALLY COUPLED IN A MANNER THAT THEIR MAGNETIC FIELDS OVERLAPS TO PRODUCE A ZONE OF ATTRACTION OF NON-MAGNETIC PARTICALS WHEN CURRENTS IN SAID EXCITATION COIL AND SAID ATTRACTOR CURRENT PATH ARE OUT OF PHASE, MEANS FOR REMOVING THE ATTRACTED OBJECTS FROM THE INFLUENCE OF SAID MAGNETIC MEANS AND MEANS FOR COLLECTING OBJECTS AFTER REMOVAL FROM SAID MAGNETIC MEANS, WHEREBY SAID ELECTRICALLY CONDUCTIVE NONMAGNETIC OBJECTS HAVE BEEN SEPARATED FROM SAID STREAM.
 2. The apparatus of claim 1 wherein said magnetic means is cylindrical in shape and mounted to be rotatable about its axis, said cylindrical magnetic means being positioned relative to said mixture guiding means so that the stream of the mixture moves in a path about a portion of an outside surface of the cylindrical magnetic means in a direction of rotatability of the outside surface.
 3. Apparatus according to claim 2 wherein the attractor current path of each of said electromagnetic assemblies is positioned in slots adjacent the surface of the cylindrical magnet wherein a core of said cylindrical magnet is a ferromagnetic material and the attractor winding an excitor coil of each of the plurality of electromagnetic assemblies are positioned parallel to the axis of rotation of said cylindrical coil within slots of said magnetic material core into the cylindrical surface which extend along its length.
 4. Apparatus according to claim 3 wherein each of said electromagnetic assemblies additionally includes a pair of spaced apart parallel slots in which the attractor electrical current path is positioned with said excitor coil being formed in a pair of slots adjacent and parallel to said attractor current loop slots but to the outside thereof, said pair of excitor coil slots of each said electromagnetic assemblies additionally receiving a portion of the excitation coils of the electromagnetic assemblies on either side thereof, whereby the zones of attraction of non-magnetic metal are formed substantially continuously around said cylinder with only small areas of repulsion between each of said zones of attraction.
 5. Apparatus according to claim 2 wherein said cylindrical magnet comprises: a large number of circular magnetic material sheets held together at their center at the axis of rotation and perpendicular thereto, such sheets having two distinct diameters and being arranged to form a plurality of spools along the length of the cylindrical magnet that are separated by walls of the larger diameter magnetic discs, a plurality of exciting windings contained individually in every third spool along the length of said cylindrical magnet, said excitor windings being electrically connected so that current flows in opposite directions in adjacent excitor windings, and an attractor windings in each of the spools contained between two of said excitor windings, whereby a zone of attraction of non-magnetic metal pieces is formed around said cylindrical magnet across said attractor windings with repulsion areas between said attraction zones.
 6. Apparatus according to claim 2 which additionally comprises magnetic material positioned immediately adjacent substantially all of the cylindrical magnet outside surface over which waste material doEs not travel, whereby the current in said excitor windings is reduced when in the region of said magnetic path material.
 7. Apparatus for separating non-magnetic metal pieces from a mixture including other types of objects, comprising: a cylindrical magnet characterized by a plurality of zones of attraction of non-magnetic metal pieces toward said cylindrical magnet, said zones covering a significant amount of the outside surface of said cylindrical magnet, said cylindrical magnet including a plurality of electromagnetic assemblies positioned adjacent one another across the surface of said cylindrical electromagnet, each of said electromagnetic assemblies including an excitation coil and an attractor electrical current path electrically isolated from one another but arranged to be magnetically coupled and to have a region adjacent the cylindrical surface where magnetic fields therefrom overlap to produce one of said zones of attraction when currents in said excitation coil and said attractor electrical current path are out of phase, and a flexible elongated conveyor contacting at least a portion of the outside surface of said cylindrical magnet in a manner to change conveyor direction and also in a manner to rotate said magnet in response to linear motion of the conveyor, whereby non-magnetic metal pieces within a mixture including other types of objects are drawn against said conveyor belt at its region contacting said cylindrical magnet while certain other types of objects are not.
 8. Apparatus for separating non-magnetic metal pieces from a mixture including other types of objects, comprising: a cylindrical magnet characterized by a plurality of zones of attraction of non-magnetic metal pieces toward said cylindrical magnet, said zones covering a significant amount of the outside surface of said cylindrical magnet, said cylindrical magnet including a plurality of electromagnetic assemblies positioned adjacent one another across the surface of said cylindrical electromagnet, each of said electromagnetic assemblies including an excitation coil and an attractor electrical current path electrically isolated from one another but arranged to be magnetically coupled and to have a region adjacent the cylindrical surface where magnetic fields therefrom overlap to produce one of said zones of attraction when currents in said excitation coil and said attractor electrical current path are out of phase, the attractor current path of each of said electromagnetic assemblies being positioned in slots adjacent the surface of the cylindrical magnet wherein a core of said cylindrical magnet is a ferro-magnetic material and the attractor current path and excitation coil of each of the plurality of electromagnetic assemblies are positioned parallel to an axis of rotation of said cylindrical coil within slots of said magnetic material core into the cylindrical surface which extend along its length, and a flexible elongated conveyor contacting at least a portion of the outside surface of said cylindrical magnet in a manner to change conveyor direction and also in a manner to rotate said magnet in response to linear motion of the conveyor, whereby non-magnetic metal pieces within a mixture including other types of objects are drawn against said conveyor belt at its region contacting said cylindrical magnet while certain other types of objects are not.
 9. Apparatus according to claim 8 wherein each of said electromagnetic assemblies additionally includes a pair of spaced apart parallel slots in which the attractor electrical current path is positioned with said excitor coil being formed in a pair of slots adjacent and parallel to said attractor current loop slots but to the outside thereof, said pair of excitor coil slots of each said electromagnetic assemblies additionally receiving a portion of the excitation coils of the electromagnetic assemblies on either side thereof, whereby the zones of attraction of non-magnetic metal are formed substantially continuously arOund said cylinder with only small areas of repulsion between each of said zones of attraction.
 10. Apparatus for separating non-magnetic metal pieces from a mixture including other types of objects, comprising: a cylindrical magnet characterized by a plurality of zones of attraction of non-magnetic metal pieces toward said cylindrical magnet, said zones covering a significant amount of the outside surface of said cylindrical magnet, said cylindrical magnet comprising: a large number of circular magnetic material sheets held together at their center at the axis of rotation and perpendicular thereto, such sheets having two distinct diameters and being arranged to form a plurality of spools along the length of the cylindrical magnet that are separated by walls of the larger diameter magnetic discs, a plurality of exciting windings contained individually in every third spool along the length of said cylindrical magnet, said excitor windings being electrically connected so that current flows in opposite directions in adjacent excitor windings, and an attractor windings in each of the spools contained between two of said excitor windings, whereby a zone of attraction of non-magnetic metal pieces is formed around said cylindrical magnet across said attractor windings with repulsion areas between said attraction zones, and a flexible elongated conveyor contacting at least a portion of the outside surface of said cylindrical magnet in a manner to change conveyor direction and also in a manner to rotate said magnet in response to linear motion of the conveyor, whereby non-magnetic metal pieces within a mixture including other types of objects are drawn against said conveyor belt at its region contacting said cylindrical magnet while certain other types of objects are not.
 11. Apparatus according to claim 10 which additionally comprises: diverters adjacent said conveyor upstream of said cylindrical magnet, said mechanical diverters positioned to form a stream of material mixture into individual streams that pass over said cylindrical magnet within its zones of attraction of non-magnetic metal particles.
 12. Apparatus for separating non-magnetic metal pieces from a mixture including other types of objects, comprising: a cylindrical magnet characterized by a plurality of zones of attraction of non-magnetic metal pieces toward said cylindrical magnet, said zones covering a significant amount of the outside surface of said cylindrical magnet, a flexible elongated conveyor contacting at least a portion of the outside surface of said cylindrical magnet in a manner to change conveyor direction and also in a manner to rotate said magnet in response to linear motion of the conveyor, whereby non-magnetic metal pieces within a mixture including other types of objects are drawn against said conveyor belt at its region contacting said cylindrical magnet while certain other types of objects are not, and magnetic material positioned immediately adjacent substantially all of the cylindrical magnet outside surface that is not contacted by said conveyor belt, whereby the current in said excitor windings is reduced when in the region of said magnetic path material. 